In my avian development work, we plan to explore whether females at the subspecies border influence male song development in different ways than nonborder populations by playing back song and by looking at female modifiability. We hope to discover the basis of the differences found between these two populations within the same subspecies. We are also studying male song perception by housing males with females with known song preferences and by housing males in groups to determine how such social influences affect repertoire development. In my infant vocal development work, we are investigating the infant's comprehension of infant vocal signals; in particular, vocal signals that are considered precursors to formal language (e.g., sounds that indicate requests, protests, deixis, emotional states, or early attempts at naming. Infants ranging in age from 6 - 18 months are used. In the first part, we have adopted Spelke's procedure to expose infants to two videotapes side-by-side in front of the infants at the same time as a soundtrack appropriate to only one of the videotapes is played back through a speaker in between the two monitors. We will investigate contrasts such as an infant pointing versus waving his arms as a deictic versus happy gesture. The dependent variables are latency and duration of looking to the tapes, synchrony of looking with the periodic onset of sounds that are matched to the infant's mouth movements, and infant vocalizations. The second part involves making high quality video and audio tapes of infants in the laboratory performing different tasks such as playing, fussing, exploring and interacting with familiar and unfamiliar people. We are especially curious to see how the ability to perceive communicative contrasts based on sound correlates with the ability to produce the vocal sounds themselves.